Re: A brief commentary

From:         shevell@leland.stanford.edu (Richard Shevell)
Organization: Stanford University, Dept. of Aero/Astro
Date:         07 Jul 96 14:15:59 
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In article <airliners.1996.1088@ohare.Chicago.COM>, kls@ohare.Chicago.COM
(Karl Swar
>     The safety board is also concerned that the designs of the flight
>     control, hydraulic, and electrical systems in the DC-10 aircraft
>     were such that all were affected by the pylon separation to the
>     extent that the crew was unable to ascertain the measures needed
>     to maintain control of the aircraft.
>
>
>     Therefore, the Safety Board concludes that the design and
>     interrelationship of the essential systems as they were affected
>     by the structural loss of the pylon contributed to this accident.
>
> While the improper maintenance caused the engine separation, that was
> simply a triggering event, which need not have cost 273 lives.  The
> NTSB clearly felt that the design was weak, if not outright faulty.

The NTSB report was faulty. For example there was no failure of the control
system.  The crash was due to a stall.  The airplane had flown for over 40
seconds when the pilot, trained to fly at the V2 speed(1.2 times the stall
speed), slowed down.  Because the wing leading edge had been damaged by the
trajectory of the nacelle, the stall speed was increased.  It is true that
the slat had retracted but the airplane was designed to fly at V2 even if
the slat were retracted but the leading edge damage was too much.  The
pylon was designed with a large safety factor and the engine attachments
were designed to break loose if violent engine vibrations occurred.  It is
true that the airplane was not designed to fly near the normal stall speed
with the leading edge slashed up but neither is any other airplane.

I believe one of the responses was to change the manual to tell pilots who
have acheived a safe speed not to slow down to meet some 'book' speed when
all ground obstacles have been cleared - which they were.
--
Richard Shevell
Email: shevell@leland.stanford.edu